Tube clamping means for tube bending apparatus



C. E. KLAMM May 31, 1960 TUBE CLAMPING MEANS FOR TUBE BEINDING APPARATUS Filed Sept. 20, 1955 5 Sheets-Sheet 1 j TTO/iWEKS m m m w.

Cari Z. JfZamm BY I M C. E. KLAMM May 31, 1960 TUBE; CLAMPING MEANS FOR TUBE BENDING APPARATUS Filed Sept. 20, 1955 3 Sheets-Sheet 2 INVENTOR E AZamm Carl May 31, 1960 c. E. KLAMM 2,933,565

TUBE CLAMPING MEANS FOR TUBE SENDING APPARATUS Filed Sept. 20, 1955 3 Sheets-Sheet 3 J9 INVENTOR. 44 f5 29 Carl EZJfZamm TUBE CLAMPING IVIEANS FOR TUBE BENDING APPARATUS Carl E. Klamm, Lakewood, Ohio, assignor to Parker- Hannifin Corporation, a corporation of Ohio Fiied Sept. 20, 1955, Ser. No. 535,485

12 Claims. (Cl. 153-40) The invention relates to new and useful improvements in tube bending apparatus of the type wherein there are included a turnable radius block and means for holding a tube against the block as it is being turned so as to cause the tube to be bent about and conform in curvature to an opposing surface portion of the block, and it primarily seeks to provide a novel clamping means for securely clamping a tube against the block preparatory to the bending of the same.

Tube bending devices of the general character referred to are well known, but difiiculties have been experienced in the use of such devices because of faulty construction of the means employed for holding the tube against the radius block. These devices have permitted slippage of the tubes during the bending thereof, and when such slippage is permitted, objectionable kinks and flattened places very commonly are provided in the bends. It is a purpose of the present invention to avoid these difficulties by provision of a novel clamping means for securely gripping the tube against the radius block, said clamping means being directly and removably mounted on the radius block.

Another object of the invention is to provide in a clamping means of the character stated a quickly mountable and detachable tube engaging jaw means which is selective in accordance with the size of tubes to be bent.

Another object of the invention is to provide a tube clamping means of the character stated wherein there is included an uprightly disposed, inwardly and outwardly and upwardly and downwardly swingable clamping jaw, and novel means for swinging said jaw inwardly or outwardly toward or from a tube clamping position, and downwardly or upwardly between a lowered, tube opposing position or an elevated, out-of-the-way position.

Another object of the invention is to provide a tube clamping means of the character stated wherein the uprightly disposed clamping jaw is pivoted intermediately of its ends at the outer end of elongated normally generally horizontally disposed link means swingable about a fixed pivot at its other or inner end, the jaw being swingable about its pivot on said link means while the same is in its generally horizontal position while moving inwardly or outwardly toward or from a tube clamping position, and being swingable upwardly or downwardly with the link means about its fixed pivot while moving toward or from the elevated, out-of-the-way position.

Another object of the invention is to provide a tube clamping means of the character stated wherein the clamping jaw and the supporting link pivots are so related that the movement of the clamping jaw toward and from a tube clamping position is on a short radius and provides for relatively slow motion for a relatively short distance, whereas the movement of the clamping jaw toward and from the elevated, out-of-the-way position is on a long radius and provides for relatively rapid motion for a relatively great distance.

Another object of the invention is to provide in a tube clamping means of the character stated novel means for rates Patent F 2,938,565 Farmed May 31, 1960 securely locking the clamping jaw against movement toward the elevated, out-of-the-way position until the jaw has been swung outwardly clear of the tube after having clamped it against the radius block preparatory to a bending operation.

A further object of the invention is to provide in a tube clamping means of the character stated novel means for securely locking the clamping jaw against inadvertent movement outwardly away from its tube clamping;

position.

A still further object of the invention is to provide a: tube clamping means of the character stated which issupported on a cylindrical column mountable and removable from a receiving socket on the radius block,

the block including a keyway and the clamping jaw meansincluding a key projection engageable in the keyway and effective to prevent any swinging movement of the clamp ing means about the center of said column.

With the above and other objects in view that will! hereinafter appear, the nature of the invention will be: more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawings.

In the drawings:

Figure l is a perspective view illustrating the inven-.

tion in use.

Figure 2 is an exploded perspective view illustrating the parts of the tube clamping means.

Figure 3 is a vertical cross section taken through the tube clamping means, the same being shown as mounted on a radius block and securely clamping a tube thereto.

Figure 4 is a side elevation of the clamping means in the tube clamping position illustrated in Figure 3, devices for imparting rotary movement to the radius block also being shown.

Figure 5 is a horizontal cross section taken on the line 55 on Figure 4.

Figure 6 is a fragmentary sectional view illustrating the clamping jaw of the clamping means in direct clamping engagement with a relatively large diameter tube.

Figure 7 is an edge view of the clamping means look ing toward the left at the illustration in Figure 8.

Figure 8 is a view similar to Figure 4 with the clamping means in the process of being released, the clamping jaw being in engagement with the tube prior to lug and shoulder contact effective to start the movement of the clamping jaw away from the tube.

Figure 9 is a view similar to Figure 8 showing the parts in the lug and shoulder engaging position and the clamping jaw moving away from the tube clamping contact.

Figure 10 is a view similar to Figure 9 and illustrating the clamping jaw partially swung upwardly to its out-ofthe-way position.

The improved tube clamping means forming the subject matter of the present invention is shown in combination with a tube bending apparatus including a sup porting table 5 whereon a supporting base 6 is secured.

as at 7. The base includes an upright bearing 8 in which a shaft 9 is rotatably mounted. Means is included for imparting rotary movement to the shaft 9, and the example mechanism shown herein comprises a bevel gear 10 afiixed to the lower end of the shaft 9 and engaged by' a bevel pinion 11 mounted on a horizontal shaft 12 which; is rotatable in the base bearing 13. The shaft 12 is.

per end of the shaft 9 in any approved manner, and said block is provided with a grooved peripheral surface 19 conforming to the curvature to which the tube 20 is to be bent. It will be apparent that by rotating the block 18 with a tube securely clamped thereagainst opposite the slide block 21 as shown in Figure 1, the clamped tube will be caused to move with the radius block so as to conform to the curvature of the peripheral surface 19 thereof, being bent against the grooved opposing surface of the slide 21.

The slide block 21 is grooved at 22, selective and varied sizes of the grooves being presentable for engagement with the tubes to be bent. The slide block is backed up by a slide 23 to which it is attached in selected position by the spring clip 24, the slide being guided on a track 25 along which it may be slid by the gaptive screw 26 which is operable in the fixed bearing The practice of tube bending to which reference has been made hereinabove and the mechanism thus far described, is conventional. The present invention relates to a novel means for securely clamping a tube to be bent against the peripheral surface of the radius block, said novel clamping means being directly mountable on and removable from the radius block. For this purpose, the radius block 18 is provided with a socket 28 in which to removably receive an upright, cylindrical column 29 forming a part of the novel clamping means and having an upright flat head extension 30 thereon, as will be clearly apparent by reference to Figures 2, 3 and 7 of the drawings. The extension 30 includes an outwardly and downwardly sloping top surface 31 terminating in a lock nose portion 32, and a cross pin 33 is mounted in said head in position for providing a stop means to be described hereinafter. In the removable mounting of the clamping means, the horizontal bottom surface 34 of the head 30 is engageable directly on the radius block as shown in Figure 6, or it may engage on a ring shim support 35 as shown in Figures 2 through 4.

A pair of support links 36 are provided, one thereof being disposed at each side of the head 30 in generally horizontal position. The links 36 are pivoted at their inner ends on a cross pin 37 extended through a receiving A cross pin 51 is mounted in a bore provided in the jaw 41 at the position of the hub extension 52, and said pin provides a pivotal mounting for a pair of outer toggle links 53, one such links being disposed at each side of the jaw 41. The inner ends of the links 53 are connected by a pivot pin 54 with the inner toggle link 55, the latter being disposed between the links 53 and being pivotally mounted intermediately ofits ends on a cross pin 56 traversing the bifurcated head 57. The head 57 is pivotally supported on the previously mentioned pivot pin 37 and has an operating handle or lever 58 secured thereto. The head 57 has stop shoulders 59 thereon in position for being engagea'ble with the links 53, as shown in Figure 4, and stop shoulders 66 also are provided in position for being engageable with the lugs 39 projecting from the links 36 as shown in Figures 9 and 10. It will be observed that the links 53 and 36 at opposite sides of the, clamping jaw 41 lie in common planes.

bore in the mounting column head 30, the links being secured in position on the pin b-y snap rings 38. The links are equipped with stop lugs 39 projecting from the inner ends thereof as clearly illustrated in Figures 4, 7 and 9, and at their outer ends said links are pivoted on a cross pin 40 mounted in a cross bore disposed intermediately of the upper and lower ends of an upright clamp jaw 41, the position of the links on the pin 40 also being secured by readily removable snap rings 42.

The clamping jaw 41 is equipped at its lower end with a half circular recess 43 disposed for direct clamping engagement with a tube to be bent, as in Figure 6, or for removably receiving a clamp piece 44 which may be selected as to size according to the size of tube to be bent. The clamp piece 44 has a pin projection 45 which is receivable in the recess socket 46, and it also has a socket 47 in which to receive the spring projected detent 48'carried by the jaw 41 and being retractable by manipulation of the finger piece 49. It will be apparent by reference to Figures 3 and 4 of the drawings that a clamping piece 44 of selective size can be readily snapped into position in the jaw recess 43 after the spring pin 48 has been retracted, and with the clamp piece 44 thus mounted, the spring pin can be released into the receiving socket 47 to removably secure the clamp piece in position.

The jaw 41 has an intermediate hub extension 59 in which the cross pin 40 is received and which may engage the column head 30 as a stop, or the links 36 may directly engage the radius block, when large tubes are being bent, as in Figure 6, or said links may engage the shim ring 35 when smaller tubes are beingbent:

Withthe arrangement shown in Figures 2. to 5, 8, and 9. k

The inner toggle link is equipped with a stop nose extension 61 which is engageable with an adjustable stop screw 62 carried by the head 57, as shown in Figures 3 and 4. The screw 62 may beadjusted to compensate for variations in tube size standards.

It is to be understood that all of the cross pins, like the pins 37 and 4%, are secured in position by readily removable snap rings.

The clamping jaw 41 also is equipped with a lock shoulder or key extension 63' which is disposed to lock under the nose extension 32 when the parts are in the tube clamping clamp locking condition illustrated in Figures 3 and 4.

In Figure 6 of the drawings the clamping of a large size tube is illustrated. In this illustration the recess 43 in the clamping jawdirectly contacts the tube and the keyway 64 in the radius block receives the key projection 63 provided on the clamp jaw, and this key and keyway engagement assures against any turning of the clamping means about the axis of the mounting column In Figures 3 and 4 of the drawings, the tube clamping and clamp locking condition of the apparatus is illustrated. In this condition, the tube is very securely clamped against the radius block and slippage or movement of the tube relative to the radius block and such as might result in kinking or flattening the bend in the tube as the tube is being bent is rendered impossible. It will be apparent by reference to Figures 3 and 4 of the drawings that the mere action of gravity is sufl'lcient to secure the locked condition of the parts with the novel linkage arrangement herein described when the handle or lever 58 is swung to the position illustrated, with the toggle linkage center or pin 56 well beyond the vertical plane in which the main pivot pin 37 is located. The tendency 'to move the lower or clamping end of the jaw 41 away from the tube 20 would tend to cause the upper end of the jaw 41 to swing inwardly about the center of the pin 40, the toggle link connection 54 to move downwardly and the stop nose portion 61 to move upwardly about its pivot center 56. Upward swinging of the nose 61 and swinging of the lever or handle 58 to the right from the position illustrated in Figures 3 and 4 would be prevented by the stop screw 62, and hence the tube clamped, clamp locked condition of the. parts is thus automatically secured.

By swinging the handle 58 to the right from the position illustrated in Figures 3 and 4 the head 57 would be swung about its center 37 for first bringing about a straightening of the toggle links 55, 53, as shown in Figure 8. Continued swinging of the handle 58 to the right would first cause the jaw' 41 to swing about its center 40 to move the clamping piece 44 outwardly away from the tube and to clear the key extension 63 from beneath the nose extension 32 as shown in Figure 9, and after the head shoulders 60 engage the link lugs 39 continued swinging of the handle 58 to the right will cause the jaw 41 and the suPPQrtinglinks 36 toswingupwardly about the pivot pin 37 in the manner clearly illustrated in Figure of the drawings. The swinging of the assembly from the clamp releasing position shown in Figure 9 toward the elevated, out-of-the-way position is shown as in progress in Figure 10, and this swinging can continue until the link lugs 39 engage the stop pin 33, at which time the clamping recess 43 in the jaw 41 or the clamp piece 44 will be disposed well out of the way above the plane in which the tube is disposed.

On the reverse or tube clamping movement of the handle 58, the action of the parts is reversed, the parts 57, 55, 53, 41, 36 swinging as a unit about the pivot center 37 until the downward swinging of the links 36 is stopped by contact with the shim ring or the radius block. At

this time the clamping jaw recess 43 of the clamp piece 44 will be disposed outwardly of but in line with the tube to be clamped as illustrated in Figure 9. Continued swinging of the handle 58 to the left would cause the toggle links 55 and 53 to pivot with respect to each other and assume the clamp locking position illustrated in Figures 3 and 4 as previously described. In this locked position the shoulder 59 is in contact with link 53 and the pivot 54 is over center with respect to the pivots 51 and 37, or below a line drawn through said pivots 51 and 37, as shown in Figure 4.

While one form of the invention has been shown for purposes of illustration, it is to be clearly understood that various changes in the details of construction and arrangement of parts may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. In a tube bending apparatus, the combination of a radius block, means rotatably supporting said block, means for imparting rotary movement to said block, said block having a periphery including a surface portion curved to correspond to the bend desired in a tube-to-bebent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereof and effective to prevent slippage of the tube relative to said curved surface portion prior to and during turning of the block, said radius block having a mounting bore therein disposed uprightly and in parallel spaced relation to the block axis, said clamping means being carried as a unit on a mounting column receivable and retained by gravity action alone in said bore so as to be readily removable therefrom, said clamping means including a clamping jaw and pivotally mounted linkage connected to said clamping jaw for moving said clamping jaw towards said radius block for clamping a tube between said clamping jaw and said radius block.

2. In a tube bending apparatus, the combination of a radius block, means rotatably supporting said block, means for imparting rotary movement to said block, said block having a periphery including a surface portion curved to correspond to the bend desired in a tube-to-bebent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereof and effective to prevent slippage of the tube relative to said curved surface portion prior to and during turning of the block, said clamping means including a clamping jaw having a tube gripping surface and means for moving said jaw to firmly clamp said surface against the tube-to-bebent and said tube against the radius block, said radius block having a mounting bore therein, and said clamping means being carried as a unit on a mounting column receivable in and readily removable from said bore, said radius block also having a keyway therein, and said clamping jaw having a key projection engageable in said keyway to prevent any swinging movement of the clamping means about the center of the mounting column.

3. In a tube bending apparatus, the combination of a radius block, means rotatably supporting said block, means for imparting rotary movement to said block, said block having a periphery including a surface portion curved to correspond to the bend desired in a tube-to-bebent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereof and effective to prevent slippage of the tube relative to said curved surface portion prior to and during turning of the block, said radius having a mounting bore therein disposed uprightly and in parallel spaced relation to the block axis, said clamping means being carried as a unit on a mounting column receivable and retained by gravity ac tion alone in said bore so as to be readily removable therefrom, said clamping means including a clamping jaw having a tube gripping surface and means for moving said jaw to firmly clamp said surface against the tube-to-bebent and said tube against the radius block, said radius block by reason of the removable mounting of the clamping means being usable with selective radius blocks varying in size according, to variations in tubes-to-be-bent, and said clamping jaw tube gripping surface being provided on a clamp piece having a quick detachable mounting on the jaw and being selective in accordance with variations in tubes-to-be-bent.

4. In a tube bending apparatus, the combination of a radius block, means rotatably supporting said block, means for imparting rotary movement to said block, said block having a periphery including a surface portion curved to correspond to the bend desired in a tube-to-bebent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereof and effective to prevent slippage of the tube relative to said curved surface portion prior to and during turning of the block, said clamping means including a clamping jaw having a tube gripping surface and means for moving said jaw to firmly clamp said surface. against a tube-to-be-bent and said tube against the radius block, said radius block having a mounting bore therein, said clamping means being carried as a unit on a mounting column receivable in and readily removable from said bore so as to be usable with selective radius blocks varying in size according to variations in tubes-to-be-bent, said clamping jaw gripping surface being engageable with a tube of predetermined size for secure clamping engagement therewith and having thereon a receiving socket and a projectable and retractable mounting pin, and there being included a clamp piece having a tube engaging surface selected as to size according to the size of a tube to be bent, said piece being subject to quick detachable mounting on said clamping jaw gripping surface by reason of having a mounting pin projection engageable in said socket and a receiving socket for removably receiving said projectable and retractable pin.

5. In a tube bending apparatus, the combination of a radius block, means rotatably supporting said block, means for imparting rotary movement to said block, said block having aperipheryincluding a surface portion curved to correspond to the bend desired in a tube-to-bebent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereof and effective to prevent slippage of the tube relative to said curved surface portion prior to and during turning of the block, said radius block being rotatable in a generally horizontal plane and the clamping means including an uprightly disposed clamping jaw, upper and lower sets of generally horizontally disposed link means pivotally connected with and swingably supporting the clamping jaw for movement inwardly and outwardly and upwardly and downwardly with respect to the radius block, and means having operable connection with said link means for positively swinging said jaw inwardly or outwardly toward or from tube clamping opposition to the radius block, and downwardly or upwardly between a lowered, tube opposing position or an elevated position out of the way of the tube bending zone adjacentthe plane of rotation of the radius block.

6. In a tube bending apparatus, the combination of a radius block, means rotatably supporting said block, means for imparting rotary movementto said block, said block having a periphery including a surface portion curved to correspond to the bend desired in a tube-to-bebent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereof and elfective to prevent slippage of the tube relative to said curved surface portion prior to and during turning of the block, said radius block being rotatable in a generally horizontal plane and the clamping means including an uprightly disposed clamping jaw, upper and lower sets of generally horizontally disposed link means pivotally connected with and swingably supporting the clamping jaw for movement inwardly and outwardly and upwardly and downwardly with respect tothe radius block, and means having operable connection with said link means for positively swinging said jawinwardly or outwardly toward or from tube clamping opposition to the radius block, and downwardly or upwardly between a lowered, tube opposingposition or an elevated position, out of the way of the tube bending zone adjacent the plane of rotation of the radius block, there also being included interlock means effective to prevent upward swinging'of' the clamping jaw until movement outwardly of said jaw clear of the tube has been completed.

7. In a tube bending apparatus, the combination of a radius block, means rotatably' supporting said block, means for imparting rotary movement to said block, said block having a periphery including a surface portion curved to correspond to the bend desired in a tube-to-bebent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereof and eifective to prevent slippage of the tube relative to said curved surface portion prior to and during turning of the block, said radius block being rotatable in a generally horizontal plane and the clamping means including an uprightly disposed inwardly and outwardly and upwardly and downwardly swingable clamping'jaw, and there also being-included means for swinging said jaw inwardly or outwardly toward or from tube clamping opposition to the radius block, and downwardly or upwardly, between a lowered, tube opposing position or an elevated position out of the way of the tube bending zone adjacent the plane of rotation of the radius block, said jaw'being pivoted intermediately of its ends at the outer end of elongated normally generally horizontally disposed link -means swingablev about a fixed pivot at its other or inner end and being swingable about its pivot on said link means while the link means is in its generally horizontal position while moving inwardly or outwardly toward or from a tube clamping position and also being swingable upwardly or downwardly with the link means about the fixed pivot of said link means while moving toward or from the elevated, out-of-the-way position.

8. In a tube bending apparatus, the combination of a radius block, means rotatably supporting said block, means for imparting rotary movement to said; block, said block having a periphery including a surface portion curved to correspond to the bend desired in a tube-to-bebent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereofand efiective to prevent slippage of the tube relative to said curved surface portion prior to and during turning of the block, said radius block beingrotatable in a generally horizontal plane and said clamping means including an uprightly disposed inwardly and outwardly and upwardly and downwardly swingable clamping jaw, said jaw being pivoted intermediately of its ends at the outer end of elongated normally generally horizontally disposed link means swingable about a fixed pivot at its other or inner end and being swingable about its pivot on said link means while the link means is in its generally horizontal position while moving inwardly or outwardly toward or from a tube clamping position and also being swingable upwardly or downwardly with the link means about the fixed pivot of said link means while moving toward or from the elevated, out-of-the-way position, an actuator lever including a head swingable about the pivot at the inner end of the link means, pivotally connected toggle links pivotally connected-at 'one end to said head and at the other end to the upper end of the clamping jaw so that when the lever is swung in one direction the toggle links will straighten and cause said jaw to swing about the pivotal connection at the outer end of the link means away from the tube clamping position and said toggle links will fold downwardly as the lever is swung in the opposite direction while moving the jaw in the opposite direction.

9. In a tube bending apparatus, the combination of a radius block, means rotatably supporting said block, means for imparting rotary movement to said block, said block having a periphery including a surface portion curved to correspond to the bend desired in a tube-to-bebent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereof and eifective to prevent slippage of the tube relative to said curved surface portion prior to and during turning of the block, said radius block being rotatable in a generally horizontal plane and said clamping means including an uprightly disposed inwardly and outwardly and upwardly and downwardly swingable clamping jaw, said jaw being pivoted intermediatelyof its ends at the outer end of elongated normally generally horizontally disposed link means swingable about a fixed pivot at its other or inner end and being swingable about its pivot on said link means while the link means is in its generally horizontal position while moving inwardly or outwardly toward or from a tube clamping position and also being swingable upwardly or downwardly with the link means about the fixed pivot of said link means while moving toward or from the elevated, out-of-the way position, an actuator lever including a head swingable about the pivot at the inner end of the link means, pivotally connected toggle links pivotally connected at one end to said head and at the other end to the upper end of the clamping jaw so that when the lever is swung in one direction the toggle links will straighten and cause said jaw to swing about the pivotal connection at the outer end of the link means away from the tube clamping position and said toggle links will fold downwardly as the lever is swung in the opposite direction while moving the jaw in the opposite direction, and cooperative shoulder and lug means carried respectively by the head and the link means and cooperatively engageable after a limited amount of free swinging movement of the head in the clamp releasing direction to cause the link means to swing with the head and elevate the clamping jaw to its out-of-the-way position.

10. In a tube bending apparatus, the combination of a radius block, means rotatably supporting said block, means for imparting rotary movement to said block, said block having a periphery including a surface portion curved to correspond to the bend desired in a tubeto-be-bent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereof and effective to prevent slippage of the tube relative to said curved surface portion prior to and during tuming of the block, said radius block being rotatable in a generally horizontal plane and said clamping means including an uprightly disposed inwardly and outwardly and upwardly and downwardly swingable clamping jaw, said jaw'being pivoted intermediately of its ends at the outer end of elongated normally generally horizontally {3, U disposed link means swingable about a fixed pivot at its other or inner end and being swingable about its pivot on said link means while the link means is in its generally horizontal position while moving inwardly or outwardly toward or from a tube clamping position and also being swingable upwardly or downwardly with the link means about the fixed pivot of said link means while moving toward or from the elevated, out-of-the-way position, an actuator lever including a head swingable about the pivot at the inner end of the link means, pivotally connected toggle links pivotally connected at one end to said head and at the other end to the upper end of the clamping jaw so that when the lever is swung in one direction the toggle links will straighten and cause said jaw to swing about the pivotal connection at the outer end of the link means away from the tube clamping position and said toggle links will fold downwardly as the lever is swung in the opposite direction while moving the jaw in the opposite direction, and means on said head and engageable with one of the toggle links to limit downward folding of the toggle links at a point where the pivotal connection between the toggle links is just past dead center with relation to the pivotal connection of the toggle links with the clamping jaw and the pivot about which the lever is swingable so that forces tending to move the jaw in a clamp releasing direction will tend to fold the toggle links and move the lever in a clamp holding direction.

11. In a tube bending apparatus, the combination of a radius block, means rotatably supporting said block, means for imparting rotary movement to said block, said block having a periphery including a surface portion curved to correspond to the bend desired in a tube-to-bebent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereof and efiective to prevent slippage of the tube relative to said curved surface portion prior to and during turning of the block, said radius block being rotatable in a generally horizontal plane and said clamping means including an uprightly disposed inwardly and outwardly and upwardly and downwardly swingable clamping jaw, said jaw being pivoted intermediately of its ends at the outer end of elongated normally generally horizontally disposed link means swingable about a fixed pivot at its other or inner end and being swingable about its pivot on said link means while the link means is in its generally horizontal position while moving inwardly or outwardly toward or from a tube clamping position and also being swingable upwardly or downwardly with the link means about the fixed pivot of said link means while moving toward or from the elevated, out-of-the-way position, an actuator lever including a head swingable about the pivot at the inner end of the link means, pivotally connected toggle links pivotally connected at one end to said head and at the other end to the upper end of the clamping jaw so that when the lever is swung in one direction the toggle links will straighten and cause said jaw to swing about the pivotal connection at the outer end of the link means away from the tube clamping position and said toggle links will fold downwardly as the lever is swung in the opposite direction while moving the jaw in the opposite direction, and means on said head and engageable with one of the toggle links to limit downward folding of the toggle links at a point where the pivotal connection between the toggle links is just past dead center with relation to the pivotal connection of the toggle links with the clamping jaw and the pivot about which the lever is swingable so that forces tending to move the jaw in a clamp releasing direction will tend to fold the toggle links and move the lever in a clamp holding direction, said downward fold limiting means comprising a stop screw adjustable to compensate for olf standard variations in tube sizes.

12. In a tube bending apparatus, the combination of a radius block, means rotatably supporting said block, means for imparting rotary movement to said block, said block having a periphery including a surface portion curved to correspond to the bend desired in a tube-tobe-bent, and means supported directly on the block and movable therewith for securely clamping a tube against the block periphery preparatory to turning thereof and effective to prevent slippage of the tube relative to sai curved surface portion prior to and during turning of the block, said radius block being rotatable in a generally horizontal plane and said clamping means including an uprightly disposed inwardly and outwardly and upwardly and downwardly swingable clamping jaw, said jaw being pivoted intermediately of its ends at the outer end of elongated normally generally horizontally disposed link means swingable about a fixed pivot at its other or inner end and being swingable about its pivot on said link means while the link means is in its generally horizontal position while moving inwardly or outwardly toward or from a tube clamping position and also being swingable upwardly or downwardly with the link means about the fixed pivot of said link means while moving toward or from the elevated, out-of-the-way position, an actuator lever including a head swingable about the pivot at the inner end of the link means, pivotally connected toggle links pivotally connected at one end to said head and at the other end to the upper end of the clamping jaw so that when the lever is swung in one direction the toggle links will straighten and cause said jaw to swing about the pivotal connection at the outer end of the link means away from the tube clamping position and said toggle links will fold downwardly as the lever is swung in the opposite direction while moving the jaw in the opposite direction, and means on said head and engageable with one of the toggle links to limit downward folding of the toggle links at a point where the pivotal connection between the toggle links is just past dead center with relation to the pivotal connection of the toggle links with the clamping jaw and the pivot about which the lever is swingable so that forces tending to move the jaw in a clamp releasing direction will tend to fold the toggle links and move the lever in a clamp holding direction, said radius block having a mounting bore therein, and said clamping means being carried as a unit on a mounting column receivable in and readily removable from said bore.

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